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Homeostasis, Thermoregulation, and Excretion
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Homeostasis, Thermoregulation, and Excretion
Homeostasis, Thermoregulation, and Excretion
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1
Question
How does a negative feedback loop restore a regulated condition?
0:55
Answer
A receptor detects a deviation from the set limits, and mechanisms act to bring the condition back within those limits. Memory hook: a thermostat notices the drift and steers the system back.
2
Question
How does positive feedback differ from negative feedback?
1:24
Answer
Positive feedback increases a deviation from its set limit; negative feedback brings a deviation back within the set limits. Memory hook: negative feedback is a brake; positive feedback is an accelerator.
3
Question
How does oxytocin amplify uterine contractions during childbirth?
1:35
Answer
The baby's head presses on the cervix, prompting oxytocin release. Oxytocin stimulates uterine contractions, which lead to more oxytocin release and further contractions. Memory hook: cervix, oxytocin, contraction, more oxytocin.
4
Question
Why must body temperature stay within a suitable range for metabolism?
2:02
Answer
At low temperatures, enzyme-controlled reactions lack sufficient kinetic energy; at high temperatures, enzymes denature. Either extreme can stop reactions and threaten cell survival.
5
Question
How do ectotherms mainly regulate their internal temperature?
2:25
Answer
They regulate it mainly through behavioral changes, although they also have some physiological responses. Memory hook: ectotherms seek suitable surroundings.
6
Question
Why do aquatic ectotherms face less temperature variation?
2:43
Answer
Water's high specific heat capacity buffers temperature changes, so aquatic environments remain relatively temperature-stable. Memory hook: water is a thermal cushion.
7
Question
How can a terrestrial ectotherm warm itself behaviorally?
3:11
Answer
It can warm itself by conduction against a hot surface, such as basking on warm ground. Memory hook: a sun-warmed rock becomes a natural heater.
8
Question
Which behaviors can help an ectotherm cool down?
3:25
Answer
It can move into shade or water, dig underground, or lie on a colder surface. Memory hook: shade, water, soil, and cool ground are four cooling stations.
9
Question
How does the nervous system coordinate endotherm temperature responses?
3:33
Answer
Skin peripheral receptors detect external temperature changes and send sensory impulses to the brain. The hypothalamus coordinates the impulses and triggers responses involving glands or muscles.
10
Question
How does vasodilation help an endotherm lose heat?
4:09
Answer
Reduced contraction of skin arterioles dilates the blood vessels, increasing blood flow near the skin surface and heat radiation. Memory hook: widened skin vessels open a wider heat exit.
11
Question
How does vasoconstriction reduce heat loss from the skin?
4:33
Answer
Greater contraction of skin arterioles constricts the vessels, reducing heat radiation from blood near the skin surface. Memory hook: narrowed vessels narrow the heat exit.
12
Question
Why does shivering increase heat production?
4:46
Answer
Repeated contraction and relaxation of skeletal muscle increases respiration, releasing more heat energy. Memory hook: shivering muscles run the body's heat-producing engine faster.
13
Question
How does raising fur or feathers help conserve heat?
5:00
Answer
Arrector pili muscles raise the fur or feathers, trapping an insulating layer of air. Lowering them when hot traps less air.
14
Question
Which behavioral responses help animals adjust to temperature?
5:24
Answer
Responses include moving into shade, removing clothes, or using a fan when hot; penguins huddle when cold. Memory hook: shade, shed, fan, huddle—three cooling actions and one warming action.
15
Question
Why must metabolic waste products be excreted?
5:46
Answer
Metabolic reactions continually produce waste products, which can become toxic if they are not removed. Excretion is the removal of these waste products.
16
Question
How is carbon dioxide produced and excreted?
5:59
Answer
Carbon dioxide is a waste product of respiration and is excreted from the lungs during exhalation.
17
Question
How does the liver convert excess dietary amino acids into urea?
6:09
Answer
Excess amino acids are broken down in the liver to ammonia, which is then converted to urea. High concentrations of urea can also be toxic, so it is excreted by the kidneys.
18
Question
Which nitrogenous waste products distinguish mammals, fish, and birds?
6:32
Answer
Mammals produce urea, fish produce ammonia, and birds produce uric acid. Memory hook: mammals use urea, fish ammonia, birds uric acid—M-F-B in that order.
19
Question
Which major functions of the liver are described?
6:43
Answer
The liver forms urea, stores glucose as glycogen, and detoxifies substances. Memory hook: the liver's three stations are urea, storage, and detoxification.
20
Question
Which blood vessels supply and drain the liver?
6:59
Answer
The hepatic artery supplies oxygenated blood, the hepatic portal vein brings blood from the digestive system, and the hepatic vein drains blood away. Memory hook: artery in, portal from digestion, hepatic vein out.
21
Question
Which structural features support hepatocytes' high metabolic rate?
7:21
Answer
Hepatocytes have many mitochondria, large nuclei, and prominent Golgi apparatus. Memory hook: many power stations, a large control center, and a prominent processing hub.
22
Question
How does blood flow through a liver lobule?
7:55
Answer
Blood from the hepatic artery and hepatic portal vein mixes in sinusoids around hepatocytes, then drains toward the hepatic vein. Memory hook: two inlets mingle in the sinusoids before the single outlet.
23
Question
How can a hepatic arteriole be distinguished from a portal venule?
9:30
Answer
The hepatic arteriole has a thicker wall than the hepatic portal venule. Memory hook: the arteriole wears the thicker wall.
24
Question
How can a bile duct be distinguished from a liver blood vessel?
10:00
Answer
The bile duct does not have a vessel wall; it is surrounded by hepatocytes. Memory hook: the duct sits among liver cells rather than wearing a vessel wall.
25
Question
How do Kupffer cells help protect the liver?
10:19
Answer
Kupffer cells in the sinusoids act like macrophages and engulf foreign particles, including pathogens entering in blood from the digestive system.
26
Question
How does bile travel from hepatocytes to the gallbladder?
10:34
Answer
Hepatocytes produce bile and secrete it into canaliculi. It drains into a bile duct and then travels to the gallbladder for storage.
27
Question
How do hepatocytes respond to insulin and glucagon?
11:35
Answer
In response to insulin, they absorb excess blood glucose and convert it to glycogen. In response to glucagon, they hydrolyze glycogen to glucose and release it into the blood.
28
Question
Which substances are named as targets of liver detoxification?
11:52
Answer
The liver neutralizes and breaks down alcohol, drugs, hormones, and toxins produced in metabolism. Memory hook: the liver's cleanup crew handles drinks, drugs, signals, and metabolic toxins.
29
Question
How does deamination produce ammonia from excess amino acids?
12:31
Answer
Deamination removes the amine group from amino acids, converting them into ammonia. Because ammonia is highly toxic, it must be converted to urea before transport in the blood.
30
Question
Which two processes are kidney functions?
13:02
Answer
The kidneys excrete urea and carry out osmoregulation, the control of blood water potential.